Over one million CT-guided biopsies are performed per year in the US. There are two million ultrasound-guided biopsies a year. Many of these ultrasound biopsies are performed because computerized tomography (“CT”) is not available. Ultrasound is also traditionally faster than CT, as there is the availability of substantially real time imaging. Traditionally, CT required the acquisition of an image, the passage of a needle, the acquisition of another image and the repositioning of the needle to be checked by acquisition of another image. With this process a biopsy could take hours and it was hard to keep track of the needle tip relative to the patient and know if it was necessary to angle up or down to get to the target.
The recent availability of CT fluoroscopy has radically changed management of patients. With CT fluoroscopy, cross sectional images of the body are obtained which are refreshed up to thirteen times a second. Further increases in the refresh rate are believed by the inventors to be a reasonable expectation. With some CT scanners three slices can be presented simultaneously, all being refreshed thirteen times a second. This can create a substantially flicker-free image of a needle or device being passed into the patient. This has the potential to increase speed, accuracy and ability to safely deliver needles to sensitive or delicate structures and avoid large blood vessels.
However, there are drawbacks and limitations to CT fluoroscopy. These mainly relate to issues of infection due to the procedure and radiation safety for the physician. For example, during the passage of the needle by the physician's hands into the patient under substantially real time x-ray guidance, the physician's hand is in the x-ray beam. This can result in an accumulation of excessive radiation dose to the physician's hand. The physician may perform the procedure repeatedly during his career or even during a single day and this cumulative dose becomes an issue of personal radiation safety.
Furthermore, current biopsy needles are composed of metal (e.g., stainless steel that generates significant artifacts when used with x-ray detectors of CT quality. These artifacts are related to the density of the metals used in these needles. These artifacts are called beam-hardening artifacts. These artifacts can obscure the intended target or obscure an important structure and possibly make it possible for inadvertent injury of the target. Accordingly, current biopsy needles are not generally suitable for CT image guided surgical procedures.
A further disadvantage of the prior art is that needles that are currently used for biopsies typically have the stylet attached to the trocar loosely, yet such a loose attachment can present certain hazards when using such a needle under CT imaging.
A further disadvantage of the prior art is that, since CT machines are typically used for simple capturing of images, they are typically non-sterile, and therefore, under CT image guidance procedures, elaborate sterilization can be necessary to reduce risk of patient infection. Simplified sterilization techniques are therefore desirable.